An equipment for drying a zone of ground weakly permeous to liquid, (especially water), is already known.
Such an equipment comprises:
a substantially air-tight membrane, covering the zone of ground to be dried and comprising a peripheral sealing means for allowing a partial vacuum to be obtained under the membrane, PA1 an embankment permeous to water and disposed under the membrane, over the zone of ground to be dried, PA1 first drain tubes disposed substantially vertically in the zone of ground and in fluid communication with the permeable embankment, PA1 second drain tubes connected to a suction pump, those second drain tubes being laid substantially flat in the embankment and in fluid communication with the liquid collected in the first drain tubes, under the membrane. PA1 effectiveness of the fluid suction, whatever the fluid may be (water, air . . . ), PA1 speed of the ground compacting effect, PA1 optimizing the arrangement of the various tubes, drain tubes, suction means, for improving the yield, PA1 optimizing the height of the embankment for combining an efficient depression of air under the membrane and a height of embankment less than a critical height possibly involving a mechanical shearing of the embankment. PA1 the second drain tubes comprise a series of drain tubes, and the distance between two such successive drain tubes of the series is about 5 to 25 times larger than the vertical distance (height) between the level of the series of second drain tubes and a maximum level of the liquid within the embankment, PA1 and the first drain tubes are separated from the second drain tubes, the liquid collected in the first drain tubes passing in the embankment before entering into the second drain tubes. PA1 the equipment further comprises complementary air suction tubes, for expelling air contained within the embankment and creating therein the air depression (in addition to, or instead of, the second drain tubes, the later being then only reserved for sucking up the water), PA1 under the membrane, at least some of those air suction tubes are connected to third drain tubes which are laid flat in the embankment and which comprise a series of fluid input holes for an input of fluid therein, PA1 the third drain tubes are disposed at a level above the level of the second drain tubes, in a zone of the embankment which is unsaturated with liquid, and those third drain tubes are connected to an air suction means. PA1 one of the third drain tubes is advantageously disposed substantially straight above one of the second drain tubes, PA1 and at least locally in the embankment, the third drain tubes are disposed every other time over the second drain tubes. PA1 disposing the first drain tubes in the zone of ground to be dried, for collecting at least the portion of the liquid to be expelled for drying the zone, PA1 disposing the second drain tubes in fluid communication with the liquid collected through the first drain tubes, while laying said second drain tubes flat over said zone of ground, within a draining embankment erected over the zone of ground to be dried and in fluid communication with the first drain tubes, PA1 covering the embankment (and thus the zone of ground to be dried) with an air-tight membrane, PA1 passing the second drain tubes through the membrane, while obtaining a sealing of said membrane, in such a way that a depression of air can be created thereunder, and PA1 sucking gaseous and liquid fluids contained in the embankment, through fluid input holes provided in the second drain tubes, for creating said depression under the membrane while expelling the liquid from the ground.
Such an assembly including an air depressed membrane is already known, especially for reinforcing weak grounds impregnated with water and having a low permeability to water.
Such grounds are improper to receive buildings thereon.
For reinforcing such grounds and improving their mechanical strength, a partial vacuum is created under the membrane.
The permeable material of the embankment is typically sand. The sand is disposed on the zone of ground to be reinforced (i.e. a layer of weak clay).